Sciency Words: Angstrom

Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:


Last week on Sciency Words, we talked about spectroscopy, a word that’s so important to the kind of space science I write about here on Planet Pailly that I’m surprised I never covered it before.

But in the interest of brevity, I had to skip a lot of the important parts of the history of spectroscopy. I mentioned Isaac Newton and Niels Bohr, but I completely skipped one of the most important “fathers of modern spectroscopy,” Swedish physicist Anders Jonas Angstrom.

Angstrom is one of those scientists who’s so important he has a unit of measure named after him: the angstrom, which equals 10-10 meters, or 0.1 nanometers, and is represented by the symbol Å (the circle over the A is a Swedish thing—Angstrom’s name is more properly spelled Ångström).

The angstrom is not officially part of the International System of Units (S.I.), but scientists use it anyway. It’s a convenient unit for measuring wavelengths of light, certain tiny crystalline structures, and other distances at the molecular and/or atomic scale.

One of the reasons Anders Angstrom features so prominently in the history of spectroscopy is that he was among the first to combine spectroscopy and photography, allowing him to not only observe a spectrum for himself but to record it for others to see.

In 1868, Angstrom published a book with the first complete map of the Sun’s spectrum in visible light, showing over 1,000 absorption lines indicating the presence of hydrogen, helium, and other elements in the Sun’s atmosphere.

This book, titled Recherches sur le Spectre Solaire (Research on the Solar Spectrum), has long since passed into the public domain, so I was able to find a copy of it available for free online. Now if only I could read French….

As one last note, in his solar spectrum book Angstrom found it convenient to quantify wavelengths of light in units equaling one ten-millionth of a meter, also known as 10-10 meters, or 0.1 nanometers. Or in other words, Anders Angstrom was the first person to measure something in angstroms.

P.S.: I really hope I got my math right for today’s cartoon.

6 thoughts on “Sciency Words: Angstrom

    1. I hadn’t really thought about it before I started researching for this post, but it makes a certain sense to me. Someone told me there’s a good rule of thumb about SI: if you never hear it with a prefix like kilo- or mili-, it’s probably not an SI unit.


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